Arthropods! - Fast Facts

Sep 28, 2026

Arthropods! introduces readers to arthropods as a vast group with more than a million species and explains key body features such as segmented parts, a back nervous system, a front heart, an outer skeleton, and multiple legs and antennae. It explains how crustaceans live, how they use exoskeletons, and why molting is risky. It also describes arachnids like spiders, scorpions, and ticks, covering leg structure, venom, lifespan, and dangers. The text compares millipedes and centipedes, their movement, defenses, and roles in gardens.

LanguageEnglish

CategoryStory & Novel

FormatPDF

Pages20

Reading Time31 min

AccessFree to download

Crustaceans

Arachnids

Millipedes and Centipedes

ArthropodsRule!by Barbara A.Roenz HOUGHTON MIFFLIN by Barbara A.Roenz 心 # HOUGHTON MIFFLIN BOSTON ILLUSTRATION CREDIT:Articulate Graphics PHOTOGRAPHY CREDITS:Cover ◎ Karen Gowlett-Holmes/Jupiter Images;tp ◎John Mitchell/Jupiter Images;3◎ KarenGowlett-Holmes/Jupiter Images;5 ◎ Craig K.Lorenz/Photo Researchers,Inc.;7 ◎John Mitchell/Jupiter Images;8 ◎StuSmucker/OnAsia/Jupiter Images;9◎ Michael Lustbader/Photo Researchers,Inc. Copyright ◎by Houghton Mifflin Company.All rights reserved. No part of this work may be reproduced or transmitted in any form or by any means,electronic or mechanical,includingphotocopying or recording,or by any information storage or retrieval system without the prior written permission of thecopyright owner unless such copying is expressly permitted by federal copyright law.With the exception of nonprofittranscription into Braille,Houghton Mifflin is not authorized to grant permission for further uses of this work.Permissionmust be obtained from the individual copyright owner as identified herein.Address requests for permission to make copiesof Houghton Miflin material to School Permissions,Houghton Miflin Company,222 Berkeley Street,Boston,MA 02116. Printed in USA ISBN-13:978-0-547-01936-9 ISBN-10:0-547-01936-X Table of Contents Crustaceans………… Arachnids…… ……5 Millipedes and Centipedes.. …7 Insects. Fast Facts. ..14 Y₀ u may think that humans rule the earthbut what organism outnumbers us?Arthropods!Arthropods represent more than a million species—more than three-fourths of Earth's creatures. The arthropod(AHR throh pahd)is a spinelessanimal with a body in parts or segments,a backnervous system,a front heart,and a skeleton onthe outside of its body.It has at least six legs,andsometimes hundreds! One type of arthropod is the crab.A crab,likea lobster or a shrimp,is a crustacean.Almost allcrustaceans live in water.All crustaceans have ten ormore legs though their body types are very different.Every crustacean also has two pairs of antennae (anTEHN neye)that some people call "feelers." Scientists have identified 38,000 different kinds ofcrustaceans.They′re important as food for birds,fish,whales,and humans worldwide. Crustaceans are faced with obstacles,howeverLike all arthropods,they have exoskeletons that donot bend and stretch,so they must exchange their old,small exoskeletons for new ones.This is a danger-ous time for crustaceans because after they shed theold exoskeleton,it takes time to grow the new one.Without hard coverings to protect them and reinforcetheir bodies,hungry animals can easily kill them. # Arachnids Another group of arthropods,the arachnids (ahRAK nid),includes spiders,scorpions,and ticks.Allarachnids have four pairs of legs.They live mostly onland,but a few kinds live in freshwater. Although many arachnids are harmless,some arepoisonous.One example of a poisonous arachnid isthe Southern black widow spider.It has a red hour-glass spot on its underside.Scorpions arearachnids that sting with their poisonoustails.Luckily,few people die from arachnid venom(VEH nuhm)if they'retreated quickly. All spiders have two main body parts and eightlegs.They also hunt and produce both silk and venom.Most aren't social and usually live only a year or two.However,tarantulas (tuh RAN choo luhz)sometimeslive for twenty years. Many spiders are black or brown,but some arebrightly colored.Others are disguised to hide themfrom enemies.One spider in Brazil looks exactly likean ant!There are more than 38,000 types of spiders,but only a few are dangerous. Most scorpions aren't dangerous,either.Allscorpion stings are painful,but only about twentyscorpion types are harmful to people.Stings fromthose scorpions can paralyze(PEHR uh leyez)victims,making them unable to move.They can also affect thevictim's heart and breathing. The word millipede comes from Latin words thatmean“thousand feet."Centipede means “hundredfeet."Many people think that millipede

FAQs

What are arthropods, and what features do they share?

Arthropods are spineless animals with bodies in segments. They have a back nervous system, a front heart, an outside skeleton, and at least six legs, often more, plus antennae.

Why is molting dangerous for crustaceans?

Crustaceans have exoskeletons that can’t bend or stretch, so they must shed old ones and grow new shells. After shedding, they are unprotected for a time, and hungry animals can kill them.

How can you tell millipedes and centipedes apart?

Millipedes move slowly in a swaying motion, while centipedes scurry quickly. Millipedes don’t bite but release a liquid that can burn skin or eyes; centipedes try to bite and can harm household insects.

Sep 28, 2026

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